#include <iostream>

using namespace std;

int main() {
    char op;
    float num1, num2;

    cout << "输入运算符：+、-、*、/ : ";
    cin >> op;

    cout << "输入两个数: ";
    cin >> num1 >> num2;

    switch (op) {
        case '+':
            cout << num1 + num2;
            break;

        case '-':
            cout << num1 - num2;
            break;

        case '*':
            cout << num1 * num2;
            break;

        case '/':
            if (num2 == 0) {
                cout << "error不能除以零";
                break;
            } else {
                cout << num1 / num2;
                break;
            }

        default:
            // 如果运算符不是 +, -, * 或 /, 提示错误信息
            cout << "Error!  请输入正确运算符。";
            break;
    }

    return 0;
}
